1. Field of the Invention
The present invention relates to a semiconductor memory device and a driving method of a semiconductor memory device.
2. Related Art
In recent years, FBC (Floating Body Cell) memory device is available as a type of semiconductor memory device expected as a memory alternative to 1T (Transistor)-1C (Capacitor) DRAM. The FBC memory device has an FET (Field Effect Transistor) including a floating body (hereinafter, also “body”) formed on an SOI (Silicon On Insulator) substrate, and stores data “1” or data “0” based on the number of majority carriers accumulated in the body.
According to a conventional FBC memory, in a data write operation during t1 and t2 (see FIG. 9), a sense amplifier once detects data within memory cells of all columns (an initial sense operation), and latches the detected data. During t3 and t5, only latched data in a selected column to be written is overwritten with external data. On the other hand, data in unselected columns not to be written is latched to a sense node in a state of the detected data. Thereafter, the sense amplifier writes (writes back) data in all columns to the memory cells.
However, in the selected column, a column select line is activated and data is transmitted from a DQ line to the sense node, after the initial sense operation. Therefore, the time of writing data into the selected memory cells becomes substantially short, in a constant write cycle time. Meanwhile, a write cycle has to be longer when a sufficient write time is attempted to be secured.